With the ever-increasing popularity and competitiveness of golf, substantial effort and resources are currently being expended to improve golf clubs. Much of the recent improvement activity has involved the combination of the use of new and increasingly more sophisticated materials in concert with advanced club-head engineering. For example, modern “wood-type” golf clubs (notably, “drivers,” “fairway woods,” and “utility or hybrid clubs”), with their sophisticated shafts and non-wooden club-heads, bear little resemblance to the “wood” drivers, low-loft long-irons, and higher numbered fairway woods used years ago. These modern wood-type clubs are generally called “metalwoods” since they tend to be made of strong, lightweight metals, such as titanium.
An exemplary metalwood golf club such as a driver or fairway wood typically includes a hollow shaft having a lower end to which the club-head is attached. Most modern versions of these club-heads are made, at least in part, of a lightweight but strong metal such as titanium alloy. In most cases, the club-head comprises a body to which a face plate (used interchangeably herein with the terms “face” or “face insert” or “striking plate” or “strike plate”) is attached or integrally formed. The strike plate defines a front surface or strike face that actually contacts the golf ball.
Some current approaches to reducing structural mass of a metalwood club-head are directed to making at least a portion of the club-head of an alternative material. Whereas the bodies and face plates of most current metalwoods are made of titanium alloy, several club-heads are available that are made, at least in part, of components formed from either graphite/epoxy-composite (or other suitable composite material) and a metal alloy. Graphite composites have a density of approximately 1.5 g/cm3, compared to titanium alloy which has a density of 4.5 g/cm3, which offers tantalizing prospects for providing more discretionary mass in the club-head.
The ability to utilize such materials to increase the discretionary mass available for placement at various points in the club-head allows for optimization of a number of physical properties of the club-head which can greatly impact the performance obtained by the user. Forgiveness on a golf shot is generally maximized by configuring the golf club head such that the center of gravity (“CG”) of the golf club head is optimally located and the moment of inertia (“MOI”) of the golf club head is maximized. However, to date there have been relatively few golf club head constructions involving a polymeric material as an integral component of the design. Although such materials possess the requisite light weight to provide for significant weight savings, it is often difficult to utilize these materials in areas of the club head subject to stresses resulting from the high speed impact of the golf ball.
For example, some current metalwoods incorporate weight tracks in the sole to support slidable weights which allow the golfer to adjust the performance characteristics of the club by changing the weight position and effective center of gravity (CG) of the club head. The weight track is generally made from cast titanium to handle the high stress resulting from the high speed impact of the golf ball. Although titanium and titanium alloys are comparatively light in the context of other metals, titanium is still relatively heavy, requires a number of reinforcing ribs and produces undesirably low first modal frequencies (when the ball is struck). A heavier construction for the weight track and ribs means less discretionary weight is available for placement in strategic locations that benefit club performance.